"The insulation was not factory installed until around 99."

????
my 92 has it my friends 91, it follows the engine, the 3.0 mounts higher than the 3.4 some models have it some do not...

if it came with it, you need it, if it did not you do not....

it is there for heat not noise, heat from 3.0 can cause damage to exterior hood paint,

best replacement since the stock only handels heat and is $200 is Cascade, Cascade is $60 and you end up with extra for the fire wall etc., it blocks heat and noise, it has a adheasive backing but I used the stock Toyota clips as well to ancor it best, also I covered the entire hood not just where the stock ont went, can also do floor boards and other stuff with the other materials there, the owner has a Taco, and there are a few customers Toys on the site, including a excab, I think it is better and eiser to deal with than dynomat, dynomat requires a hairdryer to get it soft etc. harder to work with. the Cas cade stuff is like foil covered with gummy putty, the Cascade hoodliner is like mylar covered closed cell foam.

see:
http://www.cascadeaudio.com/index.html
and
http://www.cascadeaudio.com/quotes.html
best place to buy
http://www.zeronoize.com/

their spray on stuff is cool for the under carrage as well. IMHO

 

isn't it supposed to help if your engine catches on fire too though? Flame retardant? did i spell that right? Mine has it and it was a nice yellowish color when it was new, now it's kinda brown/black looking